After heavy rainfall, the agency often issues such advisories for beaches known to have substantial stormwater runoff, which can raise bacteria levels so the waters fail to meet the New York standards for swimming, health officials said.

For recorded information on beach closings and openings in Nassau, call 516-227-9700. Health department representatives are available weekdays, from 9 a.m. to 4:45 p.m., at 516-227-9717.